Devices incorporating touchscreens have become increasingly popular owing to the increased flexibility offered by touch-based user interfaces over physical keyboards. In particular, this is the case for hand-held computing devices such as smartphones, tablet computers or simply tablets, portable media players, and the like.
A touchscreen is an electronic visual display which provides graphical information to a user and allows the user to input information to the device, or to control the device, by single touches or gestures made by touching the touchscreen. Various types of touchscreen are known, such as resistive touchscreens, surface acoustic wave touchscreens, and capacitive touchscreens.
The use of touchscreen-based devices, in particular hand-held devices, is intrinsically limited by the size of ‘interaction-space’ available to the user, i.e., the size of the touchscreen. This is the case since many users have fingers which are comparatively large in comparison to the virtual buttons which typically are presented to users of such devices. For instance, when using a virtual keyboard for entering or editing text, users often hit a key which is adjacent to the key they intended to touch.
A known solution for improving the usability of virtual keyboards is to arrange the keys on a number of separate layers between which the user may switch by means of modifier keys, thereby increasing the size of the virtual keys. However, due to the small size of touchscreens incorporated in mobile devices, in particular smartphones, the size of virtual keys is nevertheless limited, and they are typically smaller than their physical equivalents on a conventional keyboard. As a consequence, selecting the correct key may be more difficult for users, and operation of such devices is overly intricate, complex, slow, and confusing.